Rheostat



ct. 27 I MILL RHEOSTAT Filed Nov. 29, 1922 Wye 7 2 /mu;

'is preferably provided therein.

Patented Oct. 27, 1925.

UNITED STATES PATENT OFFICE.

PERCY E. MILLS, OF BROOKLYN,

NEW YORK, ASSIGNOR TO WESTERN ELECTRIC COM- PANY, INCORPORATED, OF NEW YORK, N. Y., A CORPORATION OF NEW YORK.

RHEOSTAT.

Application filed November 29, 1922. Serial No. 603,937.

To all to how it may concern:

Be it known that I, PERCY subject of the King of Great siding at Brooklyn, in the county of Kings, 5 State of New York, have invented certain new and useful Improvements in Rheostats, of which the following is a full, clear, concise, and exact description. This invention relates to. rheostats of the slidewire type in which 'a rotatable contact arm directly engages the windings of a resistance coi It is an object of the invention to simplify the construction of such a rheostat and to 1 reduce the number of parts employed therein I E. MILLS, a Britaln, re-

More specifically, the invention provides a new and improved mounting for there sistance' coil and a contact arm so constructed as to exert a constant and uniform pressure thereon.

Other features and advantages of the invention, together with the preferred arrangement of parts, will appear from a con- 2 siderationof the following description taken in connection with the accompanying draw, ing, in which:

Fig. 1 is a sectional rheostat mounted on a panel board or support.

Fig. 2 is a plan view thereof.

Fig. 3 is a perspective view of the resistance coil.

Referring to the drawing, an insulating block 5 of any suitable material, such as molded composition, is mounted by means of rivets 6 on a cup-shaped support 7 having a flange 8. The rheostat may be mounted on a panel 9 by means of bolts 10, with the flange 8 lying flat against the panel.

The resistance Wire 11 is wound uniformly upon a resilient strip of insulating material 12. The ends of the strip 12 are joined by a thin band of flexible metal 13 secured ther to by means of rivets 14. This coil may readily be slipped over the insulating block 5 to rest against a shoulder 15 which The resistance coil is mounted on the insulating block in such a way that the con- ;necting band 13 lies opposite a 'notch 16 which is formed in the block. A screw 17 is then passed through a hole 18 in the band 13 and into ahole 19 in the block 5 to tighten ing the resistance coil upon the view, showing the the band. Since the band 13 is flexible it will be drawn into the notch 16 when the screw 17 is tightened, thus drawing the ends of the strip 12 together and tightly clampblock 5. The band 13 not only serves to hold the resistance coil in position on the block 5, making it unnecessary to use additional screws or bolts, but actually serves to draw the coil around the block by simply tightening thescrew 17, thus greatly simplifying the 05 operation of mounting the coil as well as re'ucing. its cost. Furthermore, thiscoil has the advantage of being interchangeable and may readily be replaced if desired.v

An operating shaft 20 extends through a bearing Sleeve 21 in the insulating block 5 and is provided on its outer end with a knob 22 which preferably lies almost flush with the top. of the cup-shaped support 7. A contact arm 23 is keyed to the flattened end of the shaft 20 between a pair of washers 24 and 25, which are also keyed to the shaft, and is held thereto by means of a screw 26 and washer 27. The end of the contact arm 23 is looped to make contact with the re 80 sistance wire 11 on the flat side of the strip 12. By looping the contact arm instead of bending it substantially at right angles, the arm is so flexed that it will always bear snugly against the resistance wire regardless of the number of operations the device may undergo. A looped contact arm of this type maintains its springy qualities much longer than either an ordinary fiat contact arm or an arm which is'bent abruptly, as has been common practice in the past.

A'pair of terminal posts 28 and 29 are mounted on the insulating block 5, the post 28 being connected to the resistance wire- 11, and the post 29 being connected through the sleeve 21 with the contact arm 23. I A rheostat of the type described above is easily constructed because of its simplicity and because of the small number of parts employed. This rheostat may be constructed at small cost and will readily withstand a great many operations without deteriora- 2. A rheostat comprising a block, a resistance coil on said block, a flexible member joining the endsot said coil and means for distorting said flexible member to bring the ends of said resistance coil closer together thereby clampingsaid resistance coil upon'said block.

3. A rheostat comprising a block having a notch therein; a resistance coil on said block, a flexible member joining the ends of said coil, and means for depressing said member into said notch to clamp said coil on said block.

4. A rheostat comprising a block having a notch therein, a resistance coil on said block, a flexible band joining the ends of said coil adjacent said notch, and a screw member adapted when tightened to draw 5. A rheostat comprising a notch therein,

a block having a resistance 0011 on said block, a flexible band joimng the ends of said coiladjacent said notch, a screw mem-.

ber adapted when tightened to draw said 25 band into said notch thereby to clamp said coil upon said through said arm mounte block, a shaft extending block, and a flexible contact (1 on said shaft and having its end looped over said resistance coil to en- 30 gage the flat side thereof.

In witness whereo I hereunto subscribe my name this 27th day of November A. D.

PERCY E. MILLS. 

